An inspirationally sculpted backside, often, though not inevitably, female--sufficiently compelling to disencumber the customer of his (sometimes her) money or good sense. In an golden age of amateurism, perhaps obsolete.

Put on your old grey bustle
And get out and hustle
For tomorrow the rent is due!

In the fields of clover
Let the boys look you over--
If you can't get five, take two.